Re: kextunload problem

28 Jun 2006

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From: "Herb Petschauer" <bogvardi@gmail.com>
To: "Mark Stow" <markstow@hotmail.com>
CC: Darwin-kernel@lists.apple.com
Subject: Re: kextunload problem
Date: Wed, 28 Jun 2006 06:10:27 -0700
Hmm, you may need to post more details about your driver to the list.
i'm sure you're right - it'll be something silly..
Can't unload com.MyTutorial.driver.HelloIOKit due to -
com.MyTutorial.driver.HelloIOKit: com_MyTutorial_driver_HelloIOKit has 1
instance(s)
I must be doing something wrong, but i really can't think what?
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i think you've hit the nail on the head - as it works on some machines but
not others.  In the fail case i see IOResources: match category ... exists

thanks.  hopefully that's the end now.
On 28/06/06, Mark Stow <markstow@hotmail.com> wrote:

..but i've built the HelloIOKit project, and it exhibits the same symptoms
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it loads and unloads fine, but if it's in /System/Library/Extensions/ (ie

automatically loaded on boot) then it won't unload.
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From: "Herb Petschauer" <bogvardi@gmail.com>
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To: "Mark Stow" <markstow@hotmail.com>
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CC: Darwin-kernel@lists.apple.com
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Subject: Re: kextunload problem
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Date: Tue, 27 Jun 2006 08:32:30 -0700
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Hard to say, at this point it will be something silly though :-)
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It really depends on what it is you are actually implementing...
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Good luck!
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-H.
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On 27/06/06, Mark Stow <markstow@hotmail.com> wrote:
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thanks again - sorry - I've not posted anything before!
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my free() calls super::free().  In an effort to find out why it's not
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unloading, all the life cycle functions just call super (and IOLog for
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some
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diags).
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any ideas why logging out and back in again would cure this kextunload
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fail
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issue?
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From: "Herb Petschauer" <bogvardi@gmail.com>
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To: "Mark Stow" <markstow@hotmail.com>
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CC: Darwin-kernel@lists.apple.com
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Subject: Re: kextunload problem
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Date: Tue, 27 Jun 2006 07:37:40 -0700
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Ok, top posting it is...  :-)
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Look at the OSObject.cpp code, I think the retain count is set to "1"
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the
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constructor, so I would expect the release() calls to go one beyond
the
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retain() calls.
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A simple solution, does your free() method call super::free()?
That's
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my
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mistake 9 times of out 10.
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See also this thread:  <
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http://lists.apple.com/archives/darwin-drivers/2006/May/msg00091.html>
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hth,
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-H.
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On 27/06/06, Mark Stow <markstow@hotmail.com> wrote:
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Herb, thanks.  I have some more info -
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The system log tells me there is one instance of my class which is
why
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it
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can't unload.  It doesn't make any difference if the firewire device
is
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plugged in or not.
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I tried overriding retain() and release(), and in both cases when
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kextunload
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fails or succeeds, release() seems to be called once more than
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retain().
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I also noticed that if I delete the driver from
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system/library/extensions
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and reboot, so it's not loaded on boot, and then copy it back and
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kextload
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it, kextunload will succeed.
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If someone is over-retaining (and it seems to need to happen on
bootup)
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wouldn't I see a difference in the retain() release() counts when
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unload
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fails?
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From: "Herb Petschauer" < bogvardi@gmail.com>
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To: "Mark Stow" <markstow@hotmail.com>
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CC: Darwin-kernel@lists.apple.com
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Subject: Re: kextunload problem
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Date: Mon, 26 Jun 2006 09:18:45 -0700
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On 26/06/06, Mark Stow <markstow@hotmail.com > wrote:
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Hi - I'm having some difficulties with kextunload.
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I am working on a firewire device driver which derives from
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IOService.
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The
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problem seems to be that free() never gets called.  However, if I
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log
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out,
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then log back in again, everything works fine - ie free() is
called,
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and
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the
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driver unloads correctly.
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I have stripped the code down to a bare minimum of just the life
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cycle
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functions, which in turn just call into IOService.  I see init(),
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attach()
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and start() being called, and then on unload stop() detach() but
not
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free().
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Any help/ideas would be appreciated!
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Check your system.log, there's probably a message telling you why
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your
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kext
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won't unload (e.g. Couldn't unload kext (name) because there are x
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instances
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of <some class>).  free() doesn't get called until the last
release()
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(retain/release must balance) so I suspect someone is
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over-retaining().  Is
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your Firewire drive unplugged when you try and unload the kext?
The
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/dev/disk nodes are usually left created until you unplug the
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device.  Just
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a thought...
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-H.
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